Summary of Proposed Research and Objectives

Summary of Proposed Research

Functional Electrical Stimulation (FES) generally refers to the artificial electrical

stimulation of muscle which has lost nervous control, with the aim of providing muscular

contraction and producing a functionally useful movement. The proposed research project

aims to develop a Portable Programmable FES system to correct foot drop condition in

patients who have suffered motor neuron deficit. The system will be able to detect swing

phase in the subject’s gait and automatically control the electrical stimulus delivered to the

Peroneal nerve which innervates Tibialis Anterior responsible for the dorsiflexion of the

ankle. . The proposed FES system is a micro controller based surface FES system to

automatically switch on / off the electrical stimulus during the swing phase of the gait to

prevent plantar flexion (foot drop) and achieve dorsiflexion of the ankle.

Functioning of the proposed system (See fig 1) can be divided into two separate

processes namely, gait phase detection unit and Programmable Electrical Stimulator (See

fig 1). Gait phase detection unit built using foot switch and limit switch is used to detect

the swing phase of the subject’s gait. Programmable Electrical Stimulator generates the

electrical stimulus with pulse width; repetition frequency and current amplitude decided the

physiotherapist based on the adaptability of the subject. Electrical stimulus of the selected

specification will be delivered by the stimulator to the peroneal nerve only during the swing

phase of the subject’s gait.

Manual

Control

Fig. 1 : Block diagram of FES system used for Peroneal nerve stimulation

Central Controller (Microcontroller)

Electrical Stimulator

Musculoskeletal System

Gait phase detection unit

Objectives of the Proposed Research:

1. Design and develop the Programmable Stimulator using microcontroller.

2. Design and develop the gait phase detection unit using force sensor and gyroscope.

3. To use the developed FES system for the treatment of foot drop patients

A

PPENDIX II

Background and Justification for the proposed work

Background of the proposed work

Walking is the easiest way to travel short distances and plays an important role in a person

being able to do his/her daily chores conveniently. Walking being a voluntary process is

initiated and controlled by the higher centers of the nervous system. The control signals for

generating gait originate from the motor cortex of the cerebrum and these control signals

are conveyed to special neuronal circuits in the spinal cord that generate patterns of action

potentials for smooth control of different muscles to produce joint movements for walking.

The pattern of action potentials generated by the spinal cord using signals

generated from the higher centers like the motor cortex, cerebrum etc., are carried by the

motor neurons to the target muscles. The information regarding the state of the muscles

(force, length etc.) and joints are carried back to the higher centers by the sensory

neurons. This sensory information will be used by the cerebrum to modify the control

signals for spinal cord for smooth and coordinated movement of the joints.

The pattern of how a person walks is called the gait. Gait abnormality is an

unusual and unpredictable problem associated with walking. Gait abnormalities manifest

themselves as changes in the individual gait pattern. Fig. 2 shows the normal gait cycle.

One of the common gait abnormalities is foot drop or drop foot condition. Foot drop is

the paralysis or weakness of the dorsiflexor muscles of the foot and ankle, resulting in

dragging of the foot and toes. Foot drop can be a consequence of injury to muscles that

are known as dorsiflexor muscles, injury to certain nerves, a stroke, brain injury, toxic

effect of drugs, and even diabetes. In the proposed research work aims to treat the foot

drop (See fig. 3) as a result of Stroke (Cerebro Vascular Accident).

Fig. 2: Normal Gait Cycle

Foot drop affects both males and females. However, it is more common in males

(the male to female ratio is approximately 2.8:1). Both feet are equally as prone to

develop the problem. Stroke generally occurs in old age and middle age. Surgery to the

knee or leg can lead to nerve damage that then leads to the development of foot drop. For

example, approximately 0.3–4% of people who have a surgical procedure called a total

knee arthroplasty develop foot drop. People who undergo surgery to the tibia (a leg bone)

subsequently experience foot drop at a rate of 3–13%.

Fig. 3 Picture depicting foot drop

In a survey carried out by Department of Medical Physics and Biomedical

Engineering, Salisbury District Hospital, Salisbury, United Kingdom, FES was used to

treat 32 stroke patients who had a stroke for in excess of 6 months. They have constituted

two groups of subjects namely treatment group and control group. The treatment group

used the device and also received 12 sessions of physiotherapy in the first month, while

the control group who received the same contact time only received physiotherapy . After

three months of use the treatment group showed a statistically significant increase in

walking speed of 16% and a reduction in the Physiological Cost Index (PCI) of 29%

when the stimulator was used while no changes were seen in the control group. No

significant 'carryover' effect was seen although a trend was present.

There are various treatments for foot drop that depend on the specific cause of the

abnormality. Some of the possible treatments are :

Surgical treatment.

Use of orthotic device (Ankle Foot Orthosis).

Functional Electrical Stimulation.

Apart from the restoring lost functions, the use of FES has the following advantages:

Prevents muscle disuse astrophy.

Increase muscle tone.

Reduces spasticity.

Improves lost motor control.

Reducing osteoporosis and medical complications associated with immobility.

Justification of the Proposed Work

FES is a proven treatment and is widely used all over the world. Using FES is like

receiving physiotherapy every day. It has been shown to improve walking and foot drop

after a Stroke and improve walking in Multiple Sclerosis (MS). Many people have used it

to improve movement of their shoulder, elbow, wrist and fingers and to improve walking

and leg strength. Muscular pain, spasm and stiffness are often reduced as the muscles are

gently exercised and their function improves.

Type of Patients: -

Hemiplegics, Paralysis, Foot drop due to UMND and LMND.

How they will be studied: -Written informed consent would be taken,

Day 1: Connect the LED strips to the patient and make them to walk for

approximately 5m distances. Take the video of walking patient. Transfer the video

frame into computer and obtain the gait parameters like step length, stride length, and

knee angle i.e. initial values before applying stimulator. After clinical validation, start

giving the appropriate stimulator current, frequency, pulse width; reset delay using

surface electrodes for the patients.

Day 2-Day 15: Give the stimulator current using surface electrodes to the patients

and make them to walk for certain distance for 15min each day. Repeat the same for

15 days.

Day 15: Repeat the procedure of Day 1 for final values. Compare the initial and final

values of gait parameters to observe the difference in patients walking and to know

how much the stimulator is useful for the patient. Data is maintained safely for futher

use.

Fig. 4 Photograph indicating the Programmable FES system and the placement of foot

switch and limit switch.

3. Onset of the swing phase invokes the application of electrical stimulus from the

programmable stimulator to the peroneal nerve (See fig. 3 for placement of FES

electrodes) of the affected limb and the termination of the swing phase stops the

application of electrical stimulus to the target site.

Fig. 5: Placement of FES Electrode on Tibialis anterior, which is innervated by peroneal nerve

Proposal was submitted to Life Science Research Board, D.R.D.O Ministry of Defence,

New Delhi take into this consideration they have sanctioned the project under sanction

letter reference DLS/81/48222/LSRB –128/BDB/2007.